Template-removal-associated microstructural development of porous-ceramic-supported MFI zeolite membranes

Junhang Dong, Y. S. Lin, Michael Z.C. Hu, Roberta A. Peascoe, E. Andrew Payzant

Research output: Contribution to journalArticle

213 Scopus citations

Abstract

Defect-free thin MFI zeolite films were synthesized on porous α-alumina and yttria-doped zirconia (YZ) substrates by an in situ crystallization method using tetrapropylammonium hydroxide (TPAOH) as a template. The microstructure evolution of the supported zeolite films during calcination for template removal was studied by high-temperature X-ray diffraction and in situ gas permeance. Removal of the template from the zeolite films occurs at 350-500°C and is accompanied by a substantial shrinkage in the zeolite framework. After the template is removed from the zeolite at high temperatures, the zeolite crystals expand on cooling while the support shrinks. A compressive stress develops in the zeolite film during the cooling process when the zeolite crystallites are bound to the support after template removal. Without annealing prior to template removal, this stress induces cracks in the YZ-supported MFI films. High-quality MFI membranes were obtained on both α-alumina and YZ supports by using a suitable calcination temperature program. Removal of the template can either create or enlarge intercrystalline gaps as the zeolite crystallites decrease in size and draw away from adjacent crystallites. These gaps constitute the microporous non-zeolitic pores affecting the permselectivity of single-gas permeation for H2 and SF6. Both alumina- and YZ-supported MFI membranes show very good separation properties for hydrogen and n-butane mixtures, although the YZ-supported MFI films appear to have larger non-zeolitic pores than the alumina-supported membranes. (C) 2000 Elsevier Science B.V. All rights reserved.

Original languageEnglish (US)
Pages (from-to)241-253
Number of pages13
JournalMicroporous and Mesoporous Materials
Volume34
Issue number3
DOIs
StatePublished - Mar 1 2000
Externally publishedYes

Keywords

  • Calcination
  • Crack formation
  • Gas separation
  • MFI zeolite membrane
  • Thermal behavior

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials

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